1. Field of the Invention
The present invention relates generally to tamper resistant terminators and CATV coaxial connectors, and more particularly, to a tamper resistant terminator having an improved construction and sealing properties.
2. Description of the Related Art
Cable transmission systems are in wide use throughout the world for transferring television signals, and other types of signals, between devices. For example, a typical CATV system utilizes coaxial cables to provide signal communication between a head end and distributed receiver sets. A conventional CATV system includes a permanently installed cable extending from the head end throughout the area to be served. Various devices, such as directional taps, are spaced along the cable. Individual subscribers are serviced by a drop cable connected to a selected terminal of an equipment box or other device. The terminals that extend from the equipment box are externally threaded female coaxial ports designed to receive a conventional F-connector provided at the end of the drop cable. A terminator is affixed to each of the unused terminals of the equipment box to maintain proper impedance along the signal transmission path.
In some cases, the equipment box to which the drop cables are connected must be located in public areas, and the terminals may be readily accessible to the public. Such circumstances might permit unauthorized persons to move a drop cable from one port to another port, diverting service from a paying subscriber to a non-paying user. In an effort to prevent unauthorized access to the system, suppliers to the CATV industry have provided a type of terminator referred to as tamper-resistant or theft-proof. Typical examples of such tamper resistant terminators are shown and described in U.S. Pat. No. 3,845,454 (Hayward, et al.); U.S. Pat. No. 3,519,979 (Bodenstein); U.S. Pat. No. 4,469,386 (Ackerman); U.S. Pat. No. 5,055,060 (Down); U.S. Pat. No. 5,106,312 (Yeh); and U.S. Pat. No. 6,491,546 (Perry). A special tool, not generally available to the public, is required for installation and removal of such tamper resistant terminators from the equipment ports to which they are attached.
In addition, the terminals of the equipment box are often exposed to the elements. Tamper resistant terminators typically include metallic components, including an outer shell or shield intended to freely rotate about the remaining components housed therein. At least a portion of the outer shell fits closely around the internal components, but the outer shell must rotate relative to the other internal components in order for the terminator to function properly. Exposure to the elements, particularly moisture and rain, often results in corrosion of the internal components of the terminator. The result is that the outer shell locks up with the internal components whereby the entire terminator assembly can then be rotated as a unit, allowing an unauthorized person to remove the terminator without the need for any specialized tools. Some tamper-proof terminators allow for a seal to be made between the outer shell of the terminator and the female port device terminal.
Prior efforts to secure and seal such terminators have not proven to be entirely satisfactory. For example, some of such known terminators incorporate a relatively large number of components; the requirement for a relatively large number of parts, and related complex machining operations, cause the cost of production of such terminators to remain relatively high. Other versions with reduced number of components are not securely interlocked and may be defeated by simply pulling them apart.
Additionally, previous attempts at sealing the RF portion of the terminator, i.e., the portion of the terminator in electrical and mechanical contact with the female equipment port terminal, rely on a seal formed between the outer shell of the terminator and the device terminal, rather than forming a seal directly between the RF portion of the terminator and the female port. Moisture ingress between the outer shell and device terminal results in the possibility of corrosion not only in the RF interface but throughout the entire terminator. Corrosion in the RF interface may defeat the electrical termination by interfering with the proper electrical path. As mentioned above, corrosion in the remainder of the terminator may result in the fusing of the inner components and the outer shell, and thereby allow the terminator to be removed with commonly available hand tools.
It is common for coaxial terminators to be shipped from the manufacturer with the opposing ends of the terminator exposed. The equipment-side end of the terminator has an opening to extend over and engage the female equipment port, while the opposing end of the terminator includes an access hole through which the installation/removal tool is inserted. If left exposed during shipment, it is sometimes possible for the internal components of such terminators to become damaged during shipment. If such terminators are stored out in the field prior to use, or between uses, insects and other debris will often collect inside such open ends and interfere with later use of the terminator. Likewise, moisture can more easily enter inside such openings. Similarly, when such a terminator is installed over a female port terminal of the equipment box, the rear access opening often remains open, again allowing for collection of debris and the entry of moisture.
The assembly of known tamper resistant terminators is often complicated by a need to form the outer shield or shell around the internal components after the internal components are inserted therein in order to retain the internal components inside the shell following assembly. This extra manufacturing step contributes additional cost to the production of such terminators.
Accordingly, it is an object of the present invention to provide a tamper resistant coaxial terminator with a relatively small number of parts that are easy and inexpensive to produce and assemble.
Another object of the present invention is to provide such a tamper resistant coaxial terminator providing improved environmental sealing between the terminator and an equipment port terminal in a cable transmission system.
Still another object of the present invention is to provide such a tamper resistant coaxial terminator that is less subject to moisture-induced corrosion that compromises the functionality of such terminators.
A further object of the present invention is to provide a method for producing such a tamper resistant coaxial terminator in a manner that materially reduces the cost of producing a tamper-resistant termination.
A yet further object of the present invention is to provide an accessory for such terminators that protects the internal components of the terminator during shipment, while preventing dirt, debris and/or insects from collecting within the terminator during storage or actual use.
These and other objects of the present invention will become more apparent to those skilled in the art as the description of the present invention proceeds.